Parathyroid carcinoma cells obtained from a metastatic lesion in a patient with a functioning parathyroid carcinoma and severe hypercalcemia have been placed in tissue culture. After 11 cell transfers, the cells are viable. After the 5th transfer, the culture fluid was found to contain approximately 1 microgram/milliliter of human parathyroid hormone (equivalent of bovine parathyroid hormone). This application represents a supplemental request for funds to support the maintenance of these cells in culture. Should the cells survive and continue to produce parathyroid hormone, the hormone will be isolated, characterized and purified. The isolated hormone will be utilized to establish a radioimmunoassay for human parathyroid hormone. Studies will also be undertaken to assess the capacity of the parathyroid carcinoma cells in tissue culture to synthesize and secrete PTH as influenced by medium concentrations of calcium and magnesium or by the addition of various hormones or hormonal antagonists.